1. Field of the Invention
The present invention relates to an image processing apparatus for processing image data output from a sensor, such as a flat panel x-ray sensor, which senses the image of a photographic subject.
2. Description of the Related Art
When radiation rays (x-rays, xcex1 rays, xcex2 rays, xcex3 rays, electron rays, ultraviolet rays, or the like) irradiate certain phosphors, part of the irradiated energy is absorbed in the phosphors. It is known that by irradiating the phosphors with exciting light such as visible light, the phosphors exhibit photostimulated luminescence in response to the absorbed energy. Phosphors having such a property are called photostimulated phosphors. Radiation image information on a photographic subject such as a human body is temporarily stored in a photostimulated phosphor sheet. By scanning this sheet with exciting light such as a laser beam, photostimulated luminescence is produced. The light due to photostimulated luminescence is photoelectrically read and is converted into an image signal. A radiation image information recording/playback system has been proposed in which a radiation image of the subject is output based on this image signal as a visible image to a recoding material such as a photographic sensitive material or a display device such as a CRT (Cathode-Ray Tube).
Recently, apparatuses have been developed in which an x-ray image is captured using a semiconductor sensor. These apparatuses have a practical advantage over conventional radiography apparatuses using a silver-halide film in that an image can be recorded in a considerably wide radiation exposure range. Specifically, a photoelectrical converter reads x-rays having a very wide dynamic range and converts the x-rays into electrical signals. Based on the electrical signals, the radiation image is output as a visible image to the recording material such as the photographic sensitive material or the display device such as the CRT, whereby a radiation image that is not influenced by variations in the radiation exposure can be obtained.
The semiconductor sensor for sensing the x-ray image has an improved construction having a high resolution of 2000xc3x972500 pixels or above for a 14 inchxc3x9717 inch sized image. In the semiconductor sensor having such a wide sensing region, correction of each pixel is required. As the required correction, offset correction and gain correction (shading correction) can be considered. Offset correction can be performed for occurrence of each influence. An art for canceling the offset obtained over the same integration time as that of x-ray irradiation is known. On the other hand, concerning gain correction, a gain-correcting coefficient is computed by establishing an image, as a white image, obtained by irradiating x-rays without any subject to be examined. The need to frequently capture this image significantly reduces the working efficiency. Accordingly, a pre-captured gain-correcting coefficient may be used over a long period such as one week, one month, or one year. However, in view of temperature variation and deterioration over time of the sensor characteristics, frequent capture is desirable.
Capturing sometimes takes place in a state in which the sensor and the focus of the x-rays are disposed in proximity to each other. For example, in the case of x-raying bones, the distance between the sensor and the focus of the x-rays is 1 m. When a typical x-ray apparatus irradiates x-rays at 12 degrees and when the distance between the sensor and the, focus of the x-rays is 1 m, since the sensing region of the sensor is an area of 43xc3x9743 cm, irradiation cannot cover the entirety of the sensing region.
When the image of the subject is sensed under the above conditions and when correcting data is obtained, it is desirable that a correcting image be obtained by irradiating the x-rays while maintaining the above distance.
However, no appropriate correcting method of the image of the subject under the above conditions is known.
Accordingly, it is an object of the present invention to provide an image processing apparatus for appropriately correcting the image of a subject when capturing is performed in a state in which the focus of radiation rays, such as x-rays, and a sensor are disposed in proximity to each other.
To this end, according to a first aspect of the present invention, there is provided an image processing apparatus comprising a sensor including a sensing region which senses the image of an object, and a correcting circuit which performs first processing which corrects image data based on a second region corresponding to an irradiation region in the sensing region by using correcting data based on a first region corresponding to an irradiation region in the sensing region, and second processing which performs processing on the image data based on a third region included in the second region, and excluded in the overlapping part between the first region and the second region.
According to a second aspect of the present invention, an image processing apparatus comprises a sensor including a sensing region which senses the image of an object, and a correcting circuit which corrects image data based on a second region corresponding to an irradiation region in the sensing region by using correcting data based on a first region which corresponds to an irradiation region in the sensing region and which is smaller than the sensing region.
According to a third aspect of the present invention, an image processing apparatus comprises a sensor including a sensing region which senses the image of an object, and a correcting circuit which corrects image data based on a second region corresponding to an irradiation region in the sensing region by using correcting data based on a first region corresponding to an irradiation region in the sensing region, wherein the correcting circuit corrects the image data based on the fact that the irradiation region in the sensing region is smaller than the sensing region.
According to a fourth aspect of the present invention, an image processing apparatus comprises a sensor including a sensing region which senses the image of an object, a correcting circuit which corrects image data based on a second region corresponding to an irradiation region in the sensing region by using correcting data based on a first region corresponding to an irradiation region in the sensing region, and a recognizing unit which recognizes the irradiation region in the sensing region, wherein the correcting circuit corrects the image data based on the recognition result from the recognizing unit.
According to a fifth aspect of the present invention, an image processing apparatus comprises a sensor including a sensing region for sensing the image of an object, and a correcting circuit which corrects image data from the sensing region by using correcting image data based on first correcting image data and second correcting image data from the sensing region, wherein the first correcting image data and second correcting image data are obtained by different image pick up conditions.
According to a sixth aspect of the present invention, there is provided an image data correcting method for correcting image data output from a sensor including a sensing region which senses the image of an object. The image data correcting method includes correcting image data based on a second region corresponding to an irradiation region in the sensing region by using correcting data based on a first region corresponding to an irradiation region in the sensing region, and performing image processing on the image data based on a region included in the second region and excluded in the overlapping part between the first region and the second region.
According to a seventh aspect of the present invention, the image data correcting method includes correcting image data based on a second region corresponding to an irradiation region in the sensing region by using correcting data based on a first region which corresponds to an irradiation region in the sensing region and which is smaller than the sensing region.
According to an eighth aspect of the present invention, the image data correcting method includes correcting image data based on a second region corresponding to an irradiation region in the sensing region based on the fact that the irradiation region in the sensing region is smaller than the sensing region by using correcting data based on a first region corresponding to an irradiation region in the sensing region.
According to a ninth aspect of the present invention, the image data correcting method includes recognizing an irradiation region in the sensing region, and correcting image data based on a second region corresponding to the irradiation region in the sensing region based on the recognition result of the recognizing by using correcting data based on a first region corresponding to an irradiation region in the sensing region.
According to a tenth aspect of the present invention, an image data correcting method includes correcting image data from the sensing region by using correcting image data based on first correcting image data and second correcting image data from the sensing region, wherein the first correcting image data and second correcting image data are obtained by different image pick up conditions.
According to an eleventh aspect of the present invention, there is provided a computer-readable storage medium containing a program for correcting image data output from a sensor including a sensing region which senses the image of an object. The program includes a first correcting code which corrects image data based on a second region corresponding to an irradiation region in the sensing region by using correcting data based on a first region corresponding to an irradiation region in the sensing region, and a second correcting code which performs image processing on the image data based on a region included in the second region, and excluded in the overlapping part between the first region and the second region.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.